Golf Ball

ABSTRACT

The invention provides a golf ball comprising a core of at least one layer, a cover of at least one layer, and optionally an intermediate layer therebetween, characterized in that at least one layer of the core, cover and intermediate layer is formed of a golf ball-forming resin composition comprising, in admixture, (A) 100 parts by weight of a polyether ester block copolymer composed primarily of (a) high-melting crystalline polymer segments made of crystalline aromatic polyester units and (b) low-melting polymer segments made of aliphatic polyether units and (B) 0.05-10 parts by weight of a polyisocyanate compound. Using the golf ball-forming resin composition which has flexibility and high rebound resilience and is fully wear resistant, the inventive golf ball is improved in travel distance, feel, scuff resistance and impact durability.

BACKGROUND OF THE INVENTION

This invention relates to golf balls formed using golf ball-formingresin compositions which have flexibility and high rebound and are toughand fully wear resistant, and improved in travel distance, feel, scuffresistance and durability to repeated impact.

Polyether ester block copolymers comprising crystalline aromaticpolyester units such as polybutylene terephthalate units as hardsegments and aliphatic polyether units such as poly(alkylene oxide)glycols as soft segments have been of great interest as golfball-forming resin compositions because they are flexible and highlyrebound, have good mechanical properties such as strength, impactresistance and elastic recovery, and satisfactory low- andhigh-temperature properties, and are thermoplastic and easy to mold andwork. One example is the golf ball-forming resin composition describedin JP-A 7-24084.

Despite such excellent physical properties, polyether ester blockcopolymers are difficult to use as the cover because of shortage ofscuff resistance and durability to repeated impact. Heretofore, theiruse has been limited to the intermediate layer of multi-piece golf ballsincluding three- and four-piece balls. Meanwhile, ionomer resins in theform of copolymers of α-olefins and α,β-unsaturated carboxylic acidsneutralized with mono- to tri-valent metal ions have long been used asthe cover material, as described in JP-A 6-142228, because the ionomerresins are thermoplastic, easy to mold and work, very tough,unsusceptible to rupture even under considerable deformation at highspeeds, and very advantageous in improving the scuff resistance anddurability to repeated impact of golf balls.

However, these materials give a hard feel due to shortage offlexibility. It was thus proposed to use flexibilized ionomer resins inthe form of copolymers of α-olefins, α,β-unsaturated carboxylic acidsand α,β-unsaturated carboxylic acid esters neutralized with mono- totri-valent metal ions, as the golf ball-forming composition. However,such flexibilized ionomer resins are inferior in rebound,low-temperature properties and scuff resistance, with furtherimprovements being demanded.

A thermoplastic polyurethane composition made an appearance as a newcover-forming material, as described in JP-A 2004-49913. Proposedtherein was a golf ball having a good balance of flight,controllability, spin stability, feel, scuff resistance and impactdurability.

In this material, however, an attempt to render the material moreflexible in order to improve the feel can be made at the expense ofrebound and scuff resistance. Therefore, there is a desire to have acover-forming material which takes advantage of the high rebound andsoft feel of polyether ester block copolymers, and can be used tomanufacture golf balls which are good in travel distance, feel, scuffresistance and durability to repeated impact; and a golf ball having acover formed of such material.

It is noted that block copolymerized thermoplastic polyurethaneelastomers obtained by reacting polyether ester block copolymers withpolyisocyanate compounds are known as described in JP-A 52-121699 andJP-A 57-78413. Also, resin compositions comprising a polyether esterblock copolymer in admixture with a polyisocyanate compound and asilicone compound are known to have improved wear resistance asdescribed in JP-A 9-136934 and JP-A 10-101761.

Also known in the art are block copolymer thermoplastic polyurethaneelastomers which are obtained by reacting polyether ester blockcopolymers with polyisocyanate compounds for the purpose of improvingmoldability and heat resistance (see JP-A 52-121699 and JP-A 57-78413).Also known is a composition comprising a polyester block copolymer inadmixture with a specific diisocyanate compound for the purposes ofimproving flexural fatigue resistance and fisheyes during molding (seeJP-A 2004-49913). Further known are wear resistant resin compositionscomprising a polyether ester block copolymer in admixture with apolyisocyanate compound and a silicone compound (see JP-A 9-136934 andJP-A 10-101761).

All these resin compositions, however, fail to produce golf balls whichsatisfy the performance requirements including softness, high rebound,toughness and good wear resistance, and are improved in travel distance,feel, scuff resistance and durability to repeated impact.

SUMMARY OF THE INVENTION

An object of the present invention, which has been made under theabove-discussed circumstances, is to provide golf balls formed usinggolf ball-forming resin compositions which have flexibility and highrebound and are fully wear resistant, and improved in travel distance,feel, scuff resistance and impact durability.

Making extensive investigations to achieve the above object, theinventors have discovered that a golf ball-forming resin compositioncomprising, in admixture, (A) 100 parts by weight of a polyether esterblock copolymer composed primarily of (a) high-melting crystallinepolymer segments made of crystalline aromatic polyester units and (b)low-melting polymer segments made of aliphatic polyether units and (B)0.05 to 10 parts by weight of a polyisocyanate compound has flexibilityand high rebound and exhibits satisfactory wear resistance. When theabove golf ball-forming resin composition is applied as the cover of agolf ball by injection molding, the golf ball is improved in traveldistance, feel, scuff resistance and impact durability. The presentinvention is predicated on this discovery.

Accordingly, the present invention provides a golf ball as definedbelow.

[1] A golf ball comprising a core of at least one layer, a cover of atleast one layer, and optionally an intermediate layer therebetween,characterized in that

-   -   at least one layer of said core, said cover and said        intermediate layer is formed of a golf ball-forming resin        composition comprising, in admixture, (A) 100 parts by weight of        a polyether ester block copolymer composed primarily of (a)        high-melting crystalline polymer segments made of crystalline        aromatic polyester units and (b) low-melting polymer segments        made of aliphatic polyether units and (B) 0.05 to 10 parts by        weight of a polyisocyanate compound.        [2] The golf ball of claim 1, wherein said polyisocyanate        compound (B) is a polyisocyanate compound containing, on        average, more than two isocyanate groups in a molecule.        [3] The golf ball of claim 1, wherein at least 50% by weight of        said polyisocyanate compound (B) is a polyisocyanate compound        containing at least three isocyanate groups in a molecule.        [4] The golf ball of claim 1, wherein at least 70% by weight of        said polyisocyanate compound (B) is a polyisocyanate compound        containing at least three isocyanate groups in a molecule.        [5] The golf ball of claim 1, wherein a molded product molded        from said golf ball-forming resin composition by injection        molding or the like has a Shore D hardness of 25 to 85 based on        ASTM D-2240 and a rebound resilience of 40 to 90% based on        British Standard 903.        [6] The golf ball of claim 1, wherein when a molded product        molded from said golf ball-forming resin composition by        injection molding or the like is subjected to sliding wear        according to JIS K7218, Method A by rotating a hollow ring of        metal under an applied load, the molded product has a specific        wear rate, as determined under conditions: a test speed v of 0.5        m/s, a test load P of 50 N, and a sliding distance L of 3 km,        that satisfies the formula (1):        Vx=[(Wa−Wb)/(ρ·1000)]/(P·L)≦0.5  (1)        wherein Vx is a specific wear rate (mm³/(N·km) of said golf        ball-forming resin composition, Wa and Wb are the weights (mg)        of a test piece in the form of the molded product of said golf        ball-forming resin composition before and after the test,        respectively, and ρ is the density (kg/m³) of said golf        ball-forming resin composition.        [7] The golf ball of claim 1, which is a two-piece golf ball        consisting of a single layer core and a single layer cover        wherein said golf ball-forming resin composition is applied as        the material of said cover.        [8] The golf ball of claim 1, which is a three-piece golf ball        consisting of a single layer core, a single layer cover and an        intermediate layer wherein said golf ball-forming resin        composition is applied as the material of said cover.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described below in detail.

The invention provides a golf ball comprising a core of at least onelayer, a cover of at least one layer, and optionally an intermediatelayer therebetween, wherein at least one layer of the core, the coverand the intermediate layer is formed of a specific golf ball-formingresin composition. This golf ball-forming resin composition is describedin detail.

One component in the golf ball-forming resin composition is (A) apolyether ester block copolymer which is composed primarily of (a)high-melting crystalline polymer segments made of crystalline aromaticpolyester units and (b) low-melting polymer segments made of aliphaticpolyether units. The high-melting crystalline polymer segments (a) aremade of crystalline aromatic polyester units formed from an aromaticdicarboxylic acid or ester-forming derivative thereof in combinationwith an aliphatic diol, and preferably polybutylene terephthalate unitsderived from terephthalic acid and/or dimethyl terephthalate incombination with 1,4-butanediol. Also useful are polyester units derivedfrom a dicarboxylic acid component such as terephthalic acid,isophthalic acid, phthalic acid, naphthalene-2,6-dicarboxylic acid,naphthalene-2,7-dicarboxylic acid, diphenyl-4,4′-dicarboxylic acid,diphenoxyethanedicarboxylic acid, 5-sulfoisophthalic acid or anester-forming derivative thereof in combination with a diol having amolecular weight of up to 300, for example, an aliphatic diol such as1,4-butanediol, ethylene glycol, trimethylene glycol, pentamethyleneglycol, hexamethylene glycol, neopentyl glycol or decamethylene glycol,an alicyclic diol such as 1,4-cyclohexanedimethanol ortricyclodecanedimethylol, or an aromatic diol such as xylylene glycol,bis(p-hydroxy)diphenyl, bis(p-hydroxyphenyl)propane,2,2-bis[4-(2-hydroxyethoxy)phenyl]propane,bis[4-(2-hydroxy)phenyl]sulfone,1,1-bis[4-(2-hydroxyethoxy)phenyl]cyclohexane,4,4′-dihydroxy-p-terphenyl or 4,4′-dihydroxy-p-quarterphenyl. Use canalso be made of any copolymeric polyester units obtained using two ormore of the foregoing dicarboxylic acid components and diol components.In addition, polycarboxylic acid components, polyoxy acid components andpolyhydroxy components having a functionality of three or more can becopolymerized therein within a range of up to 5 mol %.

The low-melting polymer segments (b) of the polyether ester blockcopolymer (A) are units composed primarily of aliphatic polyether.Illustrative examples of the aliphatic polyether include poly(ethyleneoxide) glycol, poly(propylene oxide) glycol, poly(tetramethylene oxide)glycol, poly(hexamethylene oxide) glycol, copolymers of ethylene oxideand propylene oxide, ethylene oxide addition polymers of poly(propyleneoxide) glycol, and copolymers of ethylene oxide and tetrahydrofuran. Ofthese aliphatic polyethers, use of poly(tetramethylene oxide) glycol andethylene oxide addition polymers of poly(propylene oxide) glycol ispreferred because the resulting polyester block copolymers have betterelastic properties. The low-melting polymer segments preferably have anumber-average molecular weight of about 300 to 6,000 in thecopolymerized state.

In the polyether ester block copolymer (A), the amount of low-meltingpolymer segments (b) copolymerized is preferably in the range of 10 to80% by weight, more preferably 15 to 75% by weight.

The polyether ester block copolymer (A) is prepared by meltpolycondensation. Melt polycondensation can be performed by well-knownmethods. There may be used any of methods including, for example, amethod of effecting transesterification reaction of a lower alcoholdiester of dicarboxylic acid, an excess of a low molecular weightglycol, and a low-melting polymer segment component in the presence of acatalyst, followed by polycondensation of the resulting reactionproduct; a method of effecting esterification reaction of a dicarboxylicacid, an excess of a glycol, and a low-melting polymer segment componentin the presence of a catalyst, followed by polycondensation of theresulting reaction product; and a method of preforming high-meltingcrystalline segments, adding a low-melting segment component thereto,and effecting transesterification reaction for randomization.

The polyether ester block copolymer (A) resulting from meltpolycondensation is then processed into fine particles. Processing intofine particles may be done by a cold cut method of taking out thepolyether ester block copolymer (A) in gut or sheet form and pelletizingthe copolymer by means of a cutter; or a hot cut method of pelletizingthe copolymer without once shaping into gut or sheet form.Alternatively, fine particles may be obtained by taking out thepolyether ester block copolymer (A) in mass form, followed bypulverization.

Another component in the golf ball-forming resin composition is (B) apolyisocyanate compound, which may be a compound containing, on average,at least two isocyanate groups in a molecule. It is preferred to use apolyisocyanate compound containing, on average, more than two isocyanategroups in a molecule, and more preferably a polyisocyanate compoundcontaining at least three isocyanate groups in a molecule. It is alsoacceptable to use a mixture of a polyisocyanate compound containing twoisocyanate groups in a molecule and a polyisocyanate compound containingat least three isocyanate groups in a molecule.

Examples of the diisocyanate compound containing two isocyanate groupsin a molecule include aliphatic diisocyanates such as ethylenediisocyanate, 1,4-tetramethylene diisocyanate, ethyl(2,6-diisocyanato)hexanoate, 1,6-hexamethylene diisocyanate,1,12-dodecamethylene diisocyanate, 2,2,4- or2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate,2,6-diisocyanatomethyl caproate, bis(2-isocyanatoethyl) fumarate,bis(2-isocyanatoethyl) carbonate and2-isocyanatoethyl-2,6-diisocyanatohexanoate; alicyclic isocyanates suchas 1,3- or 1,4-bis(isocyanatemethylcyclohexane), 1,3- or1,4-diisocyanatocyclohexane,3,5,5-trimethyl(3-isocyanatomethyl)cyclohexyl isocyanate,dicyclohexylmethane-4,4′-diisocyanate, and 2,5- or2,6-diisocyanatonorbornane; aralkylene diisocyanates such as m-xylylenediisocyanate and α,α,α′,α′-tetramethyl-m-xylylene diisocyanate; andaromatic diisocyanates such as m- or p-phenylene diisocyanate,tolylene-2,4- or 2,6-diisocyanate, diphenylmethane-4,4′-diisocyanate,naphthalene-1,5-diisocyanate, diphenyl-4,4′-diisocyanate,4,4′-diisocyanato-3,3′-dimethyldiphenyl,3-methyl-diphenylmethane-4,4′-diisocyanate, and diphenylether-4,4′-diisocyanate.

Examples of the polyisocyanate compound containing at least threeisocyanate groups in a molecule include 1,3,6-hexamethylenetriisocyanate, 1,8-diisocyanato-4-isocyanatomethyloctane,2-isocyanatoethyl(2,6-diisocyanato)hexanoate, 2,5- or2,6-diisocyanatomethyl-2-isocyanatopropylnorbornane,triphenylmethanetriisocyanate, tris(isocyanatophenyl)thiophosphate, andpolymethylene polyphenylene polyisocyanate. Also included arepolyisocyanates having an isocyanurate structure resulting fromcyclo-trimerization of isocyanate groups on the foregoing diisocyanatesor triisocyanates.

The polyisocyanate compound (B) is not particularly limited as long asit contains, on average, at least two isocyanate groups in a molecule.In a preferred embodiment, at least 50% by weight of the polyisocyanatecompound used is a polyisocyanate compound containing at least threeisocyanate groups in a molecule. In a more preferred embodiment, atleast 70% by weight of the polyisocyanate compound used is apolyisocyanate compound containing at least three isocyanate groups in amolecule.

The amount of the polyisocyanate compound (B) formulated is in a rangeof 0.05 to 10 parts by weight, preferably 0.1 to 5 parts by weight, andmore preferably 0.2 to 3 parts by weight, per 100 parts by weight of thepolyether ester block copolymer (A) in pellet form. Amounts less thanthe range fail to endow the golf ball-forming resin composition withsatisfactory performance whereas amounts greater than the rangeundesirably cause the composition to gel during melt processing and thusbecome difficult to mold.

The golf ball-forming resin composition contains the above-describedcomponents (A) and (B) as essential components, and various additivesmay be incorporated therein as long as the objects of the invention arenot impaired. For example, there may be incorporated any of antioxidantssuch as well-known hindered phenols, phosphates, thioesters and aromaticamines, sun-proofing agents such as benzophenones, benzotriazoles andhindered amines, colorants such as pigments and dyes, antistatic agents,electroconductive agents, flame retardants, reinforcing agents, fillers,plasticizers, and parting agents.

The golf ball-forming resin composition is obtainable by melt mixing theabove-described components (A) and (B) while adding various additives ifnecessary, as described above. For example, the following methods (a) to(g) may be employed.

Method (a) of dry blending the polyisocyanate compound (B) in thepolyether ester block copolymer (A) and injection molding the blendwithout previous melt mixing.

Method (b) of blending the polyisocyanate compound (B) in athermoplastic resin to form master batch pellets, dry blending themaster batch pellets in the polyether ester block copolymer (A), andinjection molding the blend without previous melt mixing. It is notedthat the thermoplastic resin used in the master batch pellets shouldpreferably be fully compatible with the polyether ester block copolymer,though not limited thereto.

Method (c) of blending the polyisocyanate compound (B) in the polyetherester block copolymer (A) and feeding the blend to a screw extruderwhere they are melt mixed.

Method (d) of feeding the polyether ester block copolymer (A) to a screwextruder where it is melted, feeding the polyisocyanate compound (B) viaanother feed port, and melt mixing them.

Method (e) of blending the polyisocyanate compound (B) in athermoplastic resin to form master batch pellets, blending the masterbatch pellets in the polyether ester block copolymer (A), feeding theblend to a screw extruder, and melt mixing them. It is noted that thethermoplastic resin used in the master batch pellets should preferablybe fully compatible with the polyether ester block copolymer, though notlimited thereto.

Method (f) of blending the polyisocyanate compound (B) in the polyetherester block copolymer (A), feeding the blend to a mixer such as a rollmill, kneader or Banbury mixer, where they are melt mixed, feeding themelt to a screw extruder, and pelletizing.

Method (g) of blending the polyisocyanate compound (B) in the polyetherester block copolymer (A), feeding the blend to a mixer such as a rollmill, kneader or Banbury mixer, where they are melt mixed, taking outthe melt, cooling and pulverizing.

While the golf ball-forming resin composition comprises 100 parts byweight of the polyether ester block copolymer (A) in admixture with 0.05to 10 parts by weight of the polyisocyanate compound (B) as describedabove, a molded product molded from the golf ball-forming resincomposition by injection molding or the like should preferably have aShore D hardness of 25 to 85 based on ASTM D-2240 and a reboundresilience of 40 to 90% based on British Standard 903.

Also preferably, when a molded product molded from the golf ball-formingresin composition by injection molding or the like is subjected tosliding wear according to JIS K7218, Method A by rotating a hollow ringof metal under an applied load, the molded product has a specific wearrate, as determined under conditions: a test speed v of 0.5 m/s, a testload P of 50 N, and a sliding distance L of 3 km, that satisfies theformula (1):Vx=[(Wa−Wb)/(ρ·1000)]/(P·L)≦0.5  (1)wherein Vx is a specific wear rate (mm³/(N·km) of the golf ball-formingresin composition, Wa and Wb are the weights (mg) of a test piece in theform of the molded product of the golf ball-forming resin compositionbefore and after the test, respectively, and ρ is the density (kg/m³) ofthe golf ball-forming resin composition.

The golf ball of the invention having a ball structure that at least onelayer is formed of the aforementioned golf ball-forming resincomposition is improved in travel distance, feel, scuff resistance andimpact durability, owing to the use of the golf ball-forming resincomposition which has flexibility and high rebound and is tough andfully wear resistant.

More particularly, the golf ball of the invention, in which theaforementioned golf ball-forming resin composition is used as any ofvarious golf ball-forming materials including a core material,intermediate layer material, cover material for golf balls, one-piecegolf ball material, and solid center material (for wound golf balls),can be embodied as a two-piece golf ball consisting of a core and acover, a multi-piece golf ball comprising a core enclosed with at leasttwo layers of thermoplastic resin or rubber, a one-piece golf ball, awound golf ball or the like.

Specifically, when a solid core is made of the inventive resincomposition, it may be formed to a diameter of at least 25.00 mm,especially at least 35.00 mm, and as the upper limit, up to 39.95 mm,especially up to 38.90 mm.

In an embodiment wherein the aforementioned golf ball-forming resincomposition is used as a solid core material, an inert filler may beused for specific gravity adjustment so as to enable formation to a sizeand weight complying with the Rules of Golf. Exemplary inert fillersinclude zinc oxide, barium sulfate, silica, calcium carbonate and zinccarbonate, with barium sulfate being most preferred. The amount of thefiller blended depends on the specific gravity of the core and cover,the weight and other specifications of the ball, and is typically atleast 10 parts by weight, preferably at least 15 parts by weight, and asthe upper limit, up to 60 parts by weight, preferably up to 30 parts byweight, per 100 parts by weight of the aforementioned golf ball-formingresin composition, but not limited thereto.

In another embodiment wherein the aforementioned golf ball-forming resincomposition is used as an intermediate layer material, it may be formedto a thickness of at least 0.5 mm, preferably at least 1.0 mm, morepreferably at least 1.4 mm, and as the upper limit, up to 3.0 mm,preferably up to 2.5 mm, more preferably up to 1.9 mm. Outside therange, a greater thickness may detract from repulsion and lead to ashorter travel distance whereas a less thickness may lead to poordurability.

In a further embodiment wherein the aforementioned golf ball-formingresin composition is used as a cover material, it may be formed to athickness of at least 0.5 mm, preferably at least 1.0 mm, morepreferably at least 1.4 mm, and as the upper limit, up to 3.0 mm,preferably up to 2.5 mm, more preferably up to 1.9 mm. Outside therange, a greater thickness may detract from repulsion and lead to ashorter travel distance whereas a less thickness may lead to poordurability.

In a still further embodiment wherein the aforementioned golfball-forming resin composition is used as a one-piece golf ballmaterial, it may be sized to at least 42.60 mm, preferably at least42.65 mm, and as the upper limit, up to 42.75 mm, preferably up to 42.70mm.

In the embodiments wherein the aforementioned golf ball-forming resincomposition is used as the material for at least one layer of the ballstructure, compression or injection molding in a mold is advantageouslyemployed as the method of molding the resin composition. Injectionmolding is more advantageously employed.

The golf ball of the invention may be formed to a size and weight inaccordance with the Rules of Golf, typically to a diameter of 42.65 to42.75 mm and a weight of 45.0 to 45.5 grams.

While the golf balls of the invention may have various ball structuresin which at least one layer is formed of the aforementioned golfball-forming resin composition as described above, the invention cantake full advantage of the resin composition when the resin compositionis used as a cover material.

In manufacturing solid golf balls, the aforementioned resin compositionmay be employed as the core material, for example, although any ofcommonly used materials may also be employed. The core may be formedwhile adjusting vulcanizing conditions, formulation ratio and the like.In the core formulation, base rubber, a crosslinking agent, aco-crosslinking agent, an inert filler and the like are included. Thebase rubber used herein may be natural rubber and/or synthetic rubberwhich are conventionally used in solid golf balls although1,4-polybutadiene having at least 40% cis-configuration is preferred inthe practice of the invention. In this case, natural rubber,polyisoprene rubber, styrene-butadiene rubber or the like may be blendedin the polybutadiene if desired.

Examples of the crosslinking agent include organic peroxides such asdicumyl peroxide and di-t-butyl peroxide, with dicumyl peroxide beingmost preferred. The amount of the crosslinking agent blended may betypically at least 0.5 parts by weight, preferably at least 0.8 parts byweight and as the upper limit, up to 3 parts by weight, preferably up to1.5 parts by weight per 100 parts by weight of the base rubber.

Examples of the co-crosslinking agent include, but are not limited to,metal salts of unsaturated fatty acids, inter alia, zinc, magnesium andcalcium salts of unsaturated fatty acids of 3 to 8 carbon atoms (e.g.,acrylic acid and methacrylic acid), with the zinc salts being mostpreferred. The amount of the co-crosslinking agent blended may betypically at least 24 parts by weight, preferably at least 28 parts byweight and as the upper limit, up to 38 parts by weight, preferably upto 34 parts by weight per 100 parts by weight of the base rubber.

Examples of the inert filler include zinc oxide, barium sulfate, silica,calcium carbonate and zinc carbonate, with zinc oxide being mostcommonly used. The amount of the filler blended depends on the specificgravity of the core and cover, the weight and other specifications ofthe ball, and may be 10 to 60 parts by weight per 100 parts by weight ofthe base rubber, but not limited thereto.

A core-forming composition obtained by compounding the foregoingcomponents is kneaded in an ordinary kneader such as a Banbury mixer orroll mill, then compression or injection molded in a core-forming mold.The molded composition may be cured by heating at a sufficienttemperature for the crosslinking and co-crosslinking agents to work (forexample, about 130 to 170° C. where dicumyl peroxide and zinc acrylateare used as the crosslinking and co-crosslinking agents, respectively).

The core manufactured by compounding the foregoing components maytypically have a diameter of 38.85 to 39.95 mm, but is not limitedthereto.

A two-piece ball is manufactured from the thus obtained core by usingthe aforementioned golf ball-forming resin composition as a covermaterial, placing the core in a mold which is used in conventional golfball molding, and compression or injection molding the resin compositionin the mold to form a cover.

It is also possible to form an intermediate layer by using theaforementioned golf ball-forming resin composition as an intermediatelayer material, placing the core in a mold which is used in conventionalgolf ball molding, and compression or injection molding the resincomposition. In this embodiment, a cover material is compression orinjection molded subsequent to the intermediate layer, therebycompleting a three-piece ball. As the cover material, well-known ionomerresins are preferably used. Examples include Himilan 1554, 1557, 1601,1605, 1706, 1855, 1856, AM7315, AM7316, AM7317 and AM7318 (Dupont-MitsuiPolychemicals Co., Ltd.), and Surlyn 6320, 7930, 8120, 8945 and 9945(E.I. DuPont de Nemours and Company).

In an embodiment wherein the aforementioned golf ball-forming resincomposition is used as a cover material, a three-piece ball may bemanufactured by placing a core in a mold which is used in conventionalgolf ball molding, using a polyether ester block copolymer, for example,as an intermediate layer material, compression or injection molding thecopolymer in the mold where the core is held in place to form anintermediate layer, and thereafter compression or injection molding thegolf ball-forming resin composition as the cover material therearound toform a cover.

The enclosure with the cover is followed by deburring, pretreatment andpainting steps which may be carried out according to the conventionalgolf ball manufacturing process.

Owing to the use of a golf ball-forming resin composition which hasflexibility and high rebound and is tough and fully wear resistant, thegolf ball of the present invention is improved in travel distance, feel,scuff resistance and impact durability.

EXAMPLE

Examples and comparative examples are given below for illustrating theinvention, but the invention is not limited thereto.

As used herein, all parts and percents are by weight except for t forrebound resilience. Physical properties of resins and golf balls asreported below were measured by the following procedures.

[Melting Point]

Using a differential scanning calorimeter (Model DSC-910 by DuPont), asample was heated in a nitrogen gas atmosphere at a ramp rate of 10°C./min. The crest temperature of melting peak was measured.

[Melt Viscosity Index (MFR)]

measured under a load of 2160 g according to ASTM D-1238.

[Surface Hardness]

A hardness (Shore D hardness) was measured according to ASTM D-2240.

[Rebound Resilience]

-   -   measured according to British Standard 903.        [Specific Gravity]    -   measured according to ASTM D-792.        [Specific Wear Rate]

There was molded a disk having a diameter of 40 mm and a thickness of 3mm which was compliant with Method A of JIS K7218. Using an abrasionfriction tester (Model EFM-III-EN/F by Orientec Co., Ltd.), a slidingwear test was carried out according to JIS K7218, Method A by rotating ahollow ring of metal under an applied load on the molded disk. Aspecific wear rate as an index of wear resistance was determined underconditions: a test speed v of 0.5 m/s, a test load P of 50 N, and asliding distance L of 3 km. The specific wear rate was computedaccording to the equation:Vx=[(Wa−Wb)/(ρ·1000)]/(P·L)wherein Vx is a specific wear rate (mm³/(N·km) of the polyesterelastomer resin composition, Wa and Wb are the weights (mg) of a testpiece in the form of the molded disk of the polyester elastomer resincomposition before and after the test, respectively, and ρ is thedensity (kg/m³) of the polyester elastomer resin composition. Of theseparameters, the density ρ (kg/m³) was a value calculated as (specificgravity)/1000.[Outer Diameter]

The outer diameter (mm) of the core, intermediate layer-coated state orfinished ball was measured.

[Weight]

The weight (g) of the core, intermediate layer-coated state or finishedball was measured.

[Hardness]

An amount of deflection or deformation under a load of 100 kg of thecore, intermediate layer-coated state or finished ball was measured.Greater numerical values indicate softer states.

[Travel Distance]

Using a hitting machine (by Miyamae Co., Ltd.), a ball was hit with adriver (W#1) at a head speed of 45 m/s. A carry and a total distancewere measured.

[Durability to Repeated Impact]

Using a hitting machine (by Miyamae Co., Ltd.), a ball was repeatedlyhit with a driver (W#1) at a head speed of 45 m/s. Signs of damage byimpact were visually examined. A reference ball (Comparative Example 1)was simultaneously evaluated, and the ball was evaluated according tothe following criterion.

-   -   ◯: cracked subsequent to the reference ball    -   X: cracked prior to the reference ball        [Scuff Resistance]

A ball was conditioned at 23° C. Using a swing robot machine equippedwith a pitching wedge, the ball was hit at a head speed of 33 m/s. Signsof damage by impact were visually examined. The ball was evaluatedaccording to the following criterion.

-   -   ◯: Damage was not observed, or was of such a limited degree as        to pose no impediment to further use of the ball    -   X: serious signs of damage such as fluffed surface and chipped        dimples        [Feel]

Five top-caliber amateur golfers actually hit a ball with a driver (W#1)and rated according to the following criterion.

-   -   ⊚: very good    -   ◯: good        [Manufacture of Golf Ball Core]

Core material 1 or 2 of the formulation shown in Table 1 was kneaded andthen molded and vulcanized at 155° C. for 20 minutes, producing a solidcore No. 1 or 2 having a diameter of 38.5 mm for two-piece solid golfballs. TABLE 1 Core No. 1 No. 2 Formulation Polybutadiene rubber (BR01by JSR) 100 100 (pbw) Zinc acrylate 21.5 21.5 Dicumyl peroxide 1 1 Zincoxide 12 26.3 Vulcanizing Temperature (° C.) 155 155 conditions Time(min) 20 20 Core Specific gravity 1.07 1.16 Weight (g) 32.1 34.8 Outerdiameter (mm) 38.5 38.5 Hardness (mm) 3.4 3.4 Initial velocity (m/s)78.1 77.3[Polyether Ester Block Copolymer A]

Polyether ester block copolymers (A-1) and (A-2) which were polymerizedand pelletized as described in Reference Examples 1 and 2 were used.

Reference Example 1

A reactor equipped with a helical ribbon agitating blade was chargedwith 419 parts of terephthalic acid, 409 parts of 1,4-butanediol and 476parts of poly(tetramethylene oxide) glycol having a number averagemolecular weight of about 1,400 (Terathane 1400 by DuPont) together with2 parts of titanium tetrabutoxide. Esterification reaction was performedby heating at 190 to 225° C. for 3 hours while distilling water ofreaction out of the system.

Irganox 1010 (hindered phenol antioxidant by Ciba Geigy), 0.75 part, wasadded to the reaction mixture, which was heated at 245° C. Then thesystem was evacuated over 40 minutes to a vacuum of 27 Pa. Under theseconditions, polymerization took place for 2 hours 40 minutes, producinga polyether ester block copolymer (A-1). The polymer was ejected intowater in strands, which were cut into pellets. The pellets had a meltingpoint of 195° C., a melt viscosity index (MFR) of 18 g/10 min asmeasured at 220° C., a hardness of 47 in Shore D, and a specific gravityof 1.15.

Reference Example 2

Aside from using 444 parts of terephthalic acid, 386 parts of1,4-butanediol and 439 parts of poly(tetramethylene oxide) glycol havinga number average molecular weight of about 1,400 (PTG1400SN by HodogayaChemical Co., Ltd.), polymerization was carried out as in ReferenceExample 1, producing a polyether ester block copolymer (A-2), which wascut into pellets. The pellets had a melting point of 199° C., a meltviscosity index (MFR) of 16 g/10 min as measured at 220° C., a hardnessof 50 in Shore D, and a specific gravity of 1.17.

[Polyisocyanate Compound B]

Polyisocyanate compounds used in Examples and Comparative Examples areidentified below.

-   -   B-1: Millionate MT by Nippon Polyurethane Industry Co., Ltd.        (diphenylmethane-4,4′-diisocyanate)    -   B-2: Collonate HX by Nippon Polyurethane Industry Co., Ltd.        (polyisocyanate having an isocyanurate structure resulting from        trimerization of hexamethylenediisocyanate)    -   B-3: Millionate MR-400 by Nippon Polyurethane Industry Co., Ltd.        (polymethylene polyphenyl polyisocyanate, containing at least        71% of isocyanate having at least 3 isocyanate groups per        molecule)        [Ionomer Resin C]

Ionomer resins used in Comparative Examples are identified below.

-   -   C-1: Surlyn 8120, by DuPont, ethylene-methacrylic acid-acrylate        terpolymer ionomer, ion species Na, surface hardness (Shore D)        45    -   C-2: Himilan 1706, by Dupont-Mitsui Polychemicals Co., Ltd.,        ethylene-methacrylic acid copolymer ionomer, ion species Zn,        surface hardness (Shore D) 62    -   C-3: Himilan AM7316, by Dupont-Mitsui Polychemicals Co., Ltd.,        ethylene-methacrylic acid-acrylate terpolymer ionomer, ion        species Zn, surface hardness (Shore D) 40        [Thermoplastic Polyurethane D]

Thermoplastic polyurethane used in Comparative Examples is identifiedbelow.

-   -   D-1: MDI-PTMG type thermoplastic polyurethane elastomer

Examples 1 to 3

Using a V-blender, pellets of polyether ester block copolymer (A) whichhad been dried in hot air at 80° C. for 3 hours were dry blended withpolyisocyanate compound (B) in a blending ratio as shown in Table 2. Thedry blend was fed to a hopper of a Neomat 150/75 SYCAP-M ModelSumitomo-Netstal injection molding machine by Sumitomo Heavy Industries,Ltd. The dry blend was fed from the hopper to the chamber of the moldingmachine where it was melt mixed within the cylinder set at 240° C. andthen injection molded into a mold cavity set at 50° C. In this way, adisk-shaped product having a diameter of 100 mm and a thickness of 3 mmwas obtained. The product was held at 23° C. and 50% RH for 24 hoursbefore a specific wear rate was determined. Separately, specimens wereprepared and measured for surface hardness and rebound resilience. Theresults are also shown in Table 2.

Similarly, using a V-blender, pellets of polyether ester block copolymer(A) which had been dried in hot air at 80° C. for 3 hours were dryblended with polyisocyanate compound (B) in a blending ratio as shown inTable 2. Using an injection molding machine in which the core shown inTable 1 was held in place within a mold which was used in conventionalgolf ball molding, the blends were molded to produce two-piece golfballs as shown in Table 3. The golf balls were examined by theabove-described test procedures, with the results shown in Table 3.

Examples 4 to 8

Each of polyisocyanate compounds (B-1) to (B-3) was blended with each ofcopolymeric polyester resins to furnish three types of pelletized masterbatch having a polyisocyanate compound content of 30 wt %. Using aV-blender, pellets of polyether ester block copolymer (A) which had beendried in hot air at 80° C. for 3 hours were dry blended with thepelletized master batch of each type so that the blending ratio ofpolyether ester block copolymer (A) to polyisocyanate compound (B) wasas shown in Table 2. The dry blend was fed to a hopper of a Neomat150/75 SYCAP-M Model Sumitomo-Netstal injection molding machine bySumitomo Heavy Industries, Ltd. The dry blend was fed from the hopper tothe chamber of the molding machine where it was melt mixed within thecylinder set at 240° C. and then injection molded into a mold cavity setat 50° C. By this procedure, a disk-shaped product having a diameter of100 mm and a thickness of 3 mm was obtained. The product was held at 23°C. and 50% RH for 24 hours before a specific wear rate was determined.Separately, specimens were prepared and measured for surface hardnessand rebound resilience. The results are also shown in Table 2.

Similarly, each of polyisocyanate compounds (B-1) to (B-3) was blendedwith each of copolymeric polyester resins to furnish three types ofpelletized master batch having a polyisocyanate compound content of 30wt %. Using a V-blender, pellets of polyether ester block copolymer (A)which had been dried in hot air at 80° C. for 3 hours were dry blendedwith the pelletized master batch of each type so that the blending ratioof polyether ester block copolymer (A) to polyisocyanate compound (B)was as shown in Table 2. Using an injection molding machine in which thecore shown in Table 1 was held in place within a mold which was used inconventional golf ball molding, the blends were molded to producetwo-piece golf balls as shown in Table 3. The golf balls were examinedby the above-described test procedures, with the results shown in Table3. TABLE 2 Example Blending ratio (pbw) 1 2 3 4 5 6 7 8 Polyether esterA-1 100 — 100 — 100 100 — 100 block copolymer A-2 — 100 — 100 — — 100 —Polyisocyanate B-1 3 — — 8 — — — — compound B-2 — 1 — — 3 — — — B-3 — —1 — — 2 1 0.5 Surface hardness (Shore D) 47 52 48 50 50 50 51 49 Reboundresilience (%) 64 67 66 64 66 66 65 65 Wear Wear rate Wa-Wb 72 27 32 7735 34 22 36 resistance (mg) Specific wear 0.42 0.15 0.19 0.44 0.20 0.200.13 0.21 rate Vx (mm³/(N · km))* In Examples 4 to 8, components were formulated using the pelletizedmaster batch.

TABLE 3 Example 1 2 3 4 5 6 7 8 Core Type No. 1 No. 1 No. 1 No. 1 No. 1No. 1 No. 1 No. 1 Finished Outer diameter 42.7 42.7 42.7 42.7 42.7 42.742.7 42.7 ball (mm) Weight (g) 45.1 45.3 45.1 45.3 45.1 45.1 45.3 45.1Hardness (mm) 3.2 2.8 3.1 2.9 2.9 2.9 2.8 3.0 Initial velocity 77.4 77.377.3 77.4 77.4 77.3 77.3 77.3 (m/s) Flight Carry (m) 221 219 219 221 221220 219 218 performance Total (m) 230 228 228 230 230 229 228 226 Feel ⊚⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ Scuff resistance ◯ ◯ ◯ ◯ ◯ ◯ ◯ ◯ Durability to repeated ◯◯ ◯ ◯ ◯ ◯ ◯ ◯ impact

Examples 9 to 10

Using a V-blender, pellets of polyether ester block copolymer (A) whichhad been dried in hot air at 80° C. for 3 hours were dry blended withpolyisocyanate compound (B) in a blending ratio as shown in Table 4.Using a twin-screw extruder having a triple-thread screw with a diameterof 45 mm, the dry blend was melt mixed at 230° C. and then pelletized,obtaining a golf ball-forming resin composition. The pellets were driedin hot air at 80° C. for 3 hours and fed to a hopper of a Neomat 150/75SYCAP-M Model Sumitomo-Netstal injection molding machine by SumitomoHeavy Industries, Ltd. The dry blend was fed from the hopper to thechamber of the molding machine where it was melt mixed within thecylinder set at 240° C. and then injection molded into a mold cavity setat 50° C. In this way, a disk-shaped product having a diameter of 100 mmand a thickness of 3 mm was obtained. The product was held at 23° C. and50% RH for 24 hours before a specific wear rate was determined.Separately, specimens were prepared and measured for surface hardnessand rebound resilience. The results are also shown in Table 4.

Similarly, using a V-blender, pellets of polyether ester block copolymer(A) which had been dried in hot air at 80° C. for 3 hours were dryblended with polyisocyanate compound (B) in a blending ratio as shown inTable 4. Using a twin-screw extruder having a triple-thread screw with adiameter of 45 mm, the dry blend was melt mixed at 230° C. and thenpelletized, obtaining a golf ball-forming resin composition. The pelletswere dried in hot air at 80° C. for 3 hours. Using an injection moldingmachine in which the core shown in Table 1 was held in place within amold which was used in conventional golf ball molding, the pellets weremolded to produce two-piece golf balls as shown in Table 5. The golfballs were examined by the above-described test procedures, with theresults shown in Table 5.

Examples 11 to 12

Pellets of polyether ester block copolymer (A) which had been dried inhot air at 80° C. for 3 hours were melted by melt mixing at 240° C. for2.5 minutes in a kneader having a pair of parallel blades. To thekneader, polyisocyanate compound (B) was fed so as to give a blendingratio as shown in Table 4. Further melt mixing at 240° C. for 2.5minutes yielded a golf ball-forming resin composition. The melt mixedcomposition was taken out, ground on a grinder, and press molded into asheet. Using the pressed sheet, a surface hardness, rebound resilienceand specific wear rate were determined. The results are also shown inTable 4.

By placing the core shown in Table 1 within a mold of a compressionmolding machine which was used in conventional golf ball molding, andplacing the sheet pressed as above on the surface of the core, two-piecegolf balls as shown in Table 5 were manufactured. The golf balls wereexamined by the above-described test procedures, with the results shownin Table 5.

Comparative Examples 1 to 2

Pellets of polyether ester block copolymer (A) were dried in hot air at80° C. for 3 hours and then fed to a hopper of a Neomat 150/75 SYCAP-MModel Sumitomo-Netstal injection molding machine by Sumitomo HeavyIndustries, Ltd., without dry blending with polyisocyanate compound (B).Disks and rectangular plates were injection molded. The cylindertemperature was set at 240° C. and the mold temperature set at 50° C.The molded product was held at 23° C. and 50% RH for 24 hours before asurface hardness, rebound resilience and specific wear rate weredetermined. The results are also shown in Table 4.

Similarly, using an injection molding machine in which the core shown inTable 1 was held in place within a mold which was used in conventionalgolf ball molding, the pellets of polyether ester block copolymer (A)which had been dried in hot air at 80° C. for 3 hours were molded toproduce two-piece golf balls as shown in Table 3. The golf balls thusobtained were examined by the above-described test procedures, with theresults shown in Table 5.

Comparative Example 3

Pellets of polyether ester block copolymer (A) which had been dried inhot air at 80° C. for 3 hours were melted by melt mixing at 240° C. for2.5 minutes in a kneader having a pair of parallel blades. To thekneader, polyisocyanate compound (B) was fed so as to give a blendingratio as shown in Table 4. An attempt was made to continue melt mixingat 240° C., but the resin composition quickly gelled and stuck to theblades. A sample was scraped from the resin composition caught on theblades and examined. The sample was insoluble, infusible and notmoldable or processable, and its physical properties could not bedetermined.

Comparative Example 4

Using an ionomer resin instead of the inventive golf ball-forming resincomposition, and an injection molding machine in which the core shown inTable 1 was held in place within a mold which was used in conventionalgolf ball molding, two-piece golf balls were produced as shown in Table5. The golf balls thus obtained were examined by the above-describedtest procedures, with the results shown in Table 5. The wear test causedsubstantial wear, so that the sheet was bored during the test, with aspecific wear rate being unmeasurable.

Comparative Example 5

Using a thermoplastic polyurethane resin instead of the inventive golfball-forming resin composition, and an injection molding machine inwhich the core shown in Table 1 was held in place within a mold whichwas used in conventional golf ball molding, two-piece golf balls wereproduced as shown in Table 5. The golf balls thus obtained were examinedby the above-described test procedures, with the results shown in Table5. TABLE 4 Example Comparative Example Blending ratio (pbw) 9 10 11 12 12 3 4 5 Polyether ester A-1 100 — 100 — 100 — — block copolymer A-2 —100 — 100 — 100 100 Polyisocyanate B-1 — — — — — — — compound B-2 2 — 1— — — — B-3 — 1 — 0.3 — — 15 Ionomer resin C-1 50 C-2 35 C-3 15Thermoplastic D-1 100 polyurethane Titanium oxide 3 3 3 3 3 3 3 3 3Polyethylene wax 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 0.5 Surface hardness(Shore D) 49 51 49 50 47 50 — 50 50 Rebound resilience (%) 65 64 65 6563 63 — 50 45 Wear Wear rate Wa-Wb 36 35 14 16 176 92 — — 275 resistance(mg) Specific wear 0.21 0.2 0.08 0.09 1.02 0.52 — — 1.58 rate Vx (mm³/(N· km))

TABLE 5 Example Comparative Example 9 10 11 12 1 2 4 5 Core Type No. 1No. 1 No. 1 No. 1 No. 1 No. 1 No. 2 No. 1 Finished Outer diameter 42.742.7 42.7 42.7 42.7 42.7 42.7 42.7 ball (mm) Weight (g) 45.1 45.3 45.145.3 45.1 45.3 45.2 45.2 Hardness (mm) 3.0 2.8 3.0 2.9 3.2 2.9 2.9 2.9Initial velocity 77.3 77.3 77.3 77.3 77.2 77.2 76.8 77.0 (m/s) FlightCarry (m) 219 220 219 220 218 217 214 215 performance Total (m) 228 230228 229 226 226 224 225 Feel ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ ⊚ Scuff resistance ◯ ◯ ◯ ◯ XX ◯ ◯ Durability to repeated ◯ ◯ ◯ ◯ — X ◯ ◯ impact

As is evident from the above results, the golf ball-forming resincompositions of Examples 1 to 12 have flexibility and a high reboundresilience and are improved in wear resistance and durability torepeated impact. The inventive golf balls manufactured using the golfball-forming resin compositions of Examples 1 to 12 show a good balanceof travel distance, feel, scuff resistance and impact durability. Incontrast, the resins of Comparative Examples 1 and 2 are flexible andhigh in rebound resilience, but show a high specific wear rate or poorwear resistance and poor durability to repeated impact and are nottough. The golf balls manufactured using the resins of ComparativeExamples 1 and 2 are inferior in scuff resistance and impact durability.Both the golf ball manufactured using the ionomer resin of ComparativeExample 4 and the golf ball manufactured using the thermoplasticpolyurethane resin of Comparative Example 5 are inferior in traveldistance.

1. A golf ball comprising a core of at least one layer, a cover of atleast one layer, and optionally an intermediate layer therebetween,characterized in that at least one layer of said core, said cover andsaid intermediate layer is formed of a golf ball-forming resincomposition comprising, in admixture, (A) 100 parts by weight of apolyether ester block copolymer composed primarily of (a) high-meltingcrystalline polymer segments made of crystalline aromatic polyesterunits and (b) low-melting polymer segments made of aliphatic polyetherunits and (B) 0.05 to 10 parts by weight of a polyisocyanate compound.2. The golf ball of claim 1, wherein said polyisocyanate compound (B) isa polyisocyanate compound containing, on average, more than twoisocyanate groups in a molecule.
 3. The golf ball of claim 1, wherein atleast 50% by weight of said polyisocyanate compound (B) is apolyisocyanate compound containing at least three isocyanate groups in amolecule.
 4. The golf ball of claim 1, wherein at least 70% by weight ofsaid polyisocyanate compound (B) is a polyisocyanate compound containingat least three isocyanate groups in a molecule.
 5. The golf ball ofclaim 1, wherein a molded product molded from said golf ball-formingresin composition by injection molding or the like has a Shore Dhardness of 25 to 85 based on ASTM D-2240 and a rebound resilience of 40to 90% based on British Standard
 903. 6. The golf ball of claim 1,wherein when a molded product molded from said golf ball-forming resincomposition by injection molding or the like is subjected to slidingwear according to JIS K7218, Method A by rotating a hollow ring of metalunder an applied load, the molded product has a specific wear rate, asdetermined under conditions: a test speed v of 0.5 m/s, a test load P of50 N, and a sliding distance L of 3 km, that satisfies the formula (1):Vx=[(Wa−Wb)/(ρ·1000)]/(P·L)≦0.5  (1) wherein Vx is a specific wear rate(mm³/(N·km) of said golf ball-forming resin composition, Wa and Wb arethe weights (mg) of a test piece in the form of the molded product ofsaid golf ball-forming resin composition before and after the test,respectively, and ρ is the density (kg/m³) of said golf ball-formingresin composition.
 7. The golf ball of claim 1, which is a two-piecegolf ball consisting of a single layer core and a single layer coverwherein said golf ball-forming resin composition is applied as thematerial of said cover.
 8. The golf ball of claim 1, which is athree-piece golf ball consisting of a single layer core, a single layercover and an intermediate layer wherein said golf ball-forming resincomposition is applied as the material of said cover.